Setting data in multiple nested lists ASP.NET MVC C#

I'm an intern with very basic knowledge of ASP and C#.
I'm trying to display a list of projects > maps > thememaps in an application I'm working on in ASP.NET MVC. In my third foreach I get an error saying: "Does not contain a definition for "ThemeMaps" and no extension method "ThemeMaps" accepting a first argument of type could be found".

I'm confused as to why vmProject.Maps does not contain the property ThemeMaps. I instantiated that list just like maps. What am I doing wrong?

using Mapgear.MapViewer.Entities;
using System;
using System.Collections;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;
using System.Linq;
using System.Web;
using System.Web.Mvc;